Laboratory balance



Feb. 3, 1942.

F. W. THOMPSON LABORATORY BALANCE Filed Feb. .3, 1941 2 Sheets-Sheet 1INVENTOR. M i/cwpso/v;

ATTORNEY.

Feb. 3, 1942.

Filed Feb. 3, 1941 2 Sheets-Sheet 2 INVENTOR. f/alsp M 7/710MP50/Y.

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x m "I, 5 mm 2 H 3 w w \1 1 m Patented Feb. 3, 1942 UNITED STATES PATENTOFFlCE' LABORATORY BALANCE Fred W. Thompson, Denver, Colo.

Application February 3, 1941, Serial No. 377,156

7 Claims.

This invention relates to an analytical or laboratory balance. The usualanalytical balance is provided with a hollow shaft or pedestal risingfrom the floor within the balance case for supporting the beam pivotsand the beam lifting mechanism.

The principal object of this invention is to eliminate the post withinthe case and to support the beam and all related apparatus directly fromthe back wall of the case, such a construction results in greateraccessibility to the balance pans and to a much more economical andfacile method of manufacture.

Other objects of the invention are to provide a laboratory balance inwhich all the operating mechanism for lifting the beam will beaccessible on the exterior of the case for repair, lubrication andadjustment; to provide guide bearings for the beam lifting mechanismwhich can be quickly and easily machined without requiring micrometricboring and turning operations, which will be free from bearinglooseness, and which can be easily adjusted to take up any wear orlooseness which may occur in use.

Other objects and advantages reside in the de tail construction of theinvention, which is designed for simplicity, economy, and efficiency.These will become more apparent from the following description.

In the following detailed description of the invention reference is hadto the accompanying drawings which form a part hereof. Like numeralsrefer to like parts in all views of the drawings and throughout thedescription.

In the drawings:

Fig. 1 is a front view of a laboratory balance constructed in accordancewith the principles of this invention:

Fig. 2 is a rear view thereof;

Fig. 3 is an enlarged vertical section therethrough, taken on the line33, Fig. 1;

Fig. 4 is an enlarged fragmentary rear view with the cover plate removedto show the beam lifting rod;

Fig. 5 is a fragmentary horizontal section looking downward on the line5-5, Fig. 3;

Fig. 6 is a similar section looking downward on the line 66, Fig. 3; and

Fig. 7 is an enlarged fragmentary section taken on the line l-'l,.Fig.4, illustrating the bearing for the lifting rod employed in the improvedbalance.

The principal feature of this invention is the improved construction forsupporting and lifting the beam. The remainder of the balance may haveany standard construction. Typical standard parts of a balance aredesignated by numerals on the drawings as follows: beam l0, pans ll, panbails I2, stirrups l3, knife edges [4, bearing posts l5, pivot studs l6,beam lifting yokes ll, rider shifting rod l8, agate bearings 30, plumbline 33, plumb indicating point 34, leveling legs 35, pointer 51, andindicating scale 58.

The balance illustrated is enclosed in a glass case consisting of metalframe Hi, the sides of which contain glass panes 20 and the front ofwhich is closed by a liftable glass door enclosed in a metallic doorframe 2|. The top is covered by a metal top plate 22, and the bottom isclosed by means of a downwardly flanged floor plate 23.

The back of the case, however, is closed by two glass panes 55 which areseparated vertically at the middle of the case by means of a taperedmetallic supporting member 24 which extends as a unit from a middle leg25, which supports the case at the rear, to the top plate 22. The mem--ber 24 is secured by means of cap screws 3| to the rear flange of thefloor plate 23. It is also provided with a plumb post 32 from which theplumb line and plumb 33 depend over the indicating point 34 on thefloor.

On the front of the member 24, below the beam H], a pyramidal boss 26 isformed extending forwardly into the case. An angle bracket 21 is boltedto the boss 26 by means of suitable attachment bolts 28 and extendsforwardly in the case beneath the beam In. The two bearing posts l5 areattached to this angle bracket by means of suitable attachment screws 29and extend fixedly upward therefrom in parallel relation, terminating inthe usual agate bearings 33 for the knife edges [4. Thus, the beam andits operating mechanisms are supported in their proper position withinthe case without the use of any internal post or pedestal.

The beam lifting yokes ll are secured to the forward extremity of ahorizontal bracket member 36, preferably T-shaped in cross section,which is fixedly formed on, and at right angles to, a vertical liftingrod 31. The bracket member extends through an opening 56 in thesupporting member. The lifting rod 31 extends vertically downward in achannel formed in the rear of the member 24. The rod 31 is formed withtwo bearing portions 33, one being positioned adjacent the top of therod and one adjacent the bottom thereof. Opposite these portions of therod, the channel at the rear of the member 24 is formed With twoangularly-positioned, opposed, vertical bearing surfaces 39, againstwhich the bearing portion 38 of the rod rides.

A bearing plate 40 is secured across the channel opposite each bearingportion 38 of the rod. A U-shaped bearing piece 4| extends verticallybetween each plate 40 and the bearing portions 38 of the rod. The turnedends of the bearing pieces 4| rest in notches in the upper and loweredges of the plates 40. An adjusting screw 42 extends through each plate40, by means of which its bearing piece 4| can be brought against thebearing portion of the rod to hold the latter against its two opposedsurfaces 39 without side play and yet allowing free vertical movementthereof.

Thus, it can be seen that due to the fact that the bracket member 36 isformed at a fixed angle with the rod 31, the overhanging weight thereofis absorbed in the two three-line bearings on the rod 31, formed by theinclined channel sides and the bearing pieces 4|.

An adjustable lift screw 43 is threaded into the lower extremity of therod 31. The head of the screw 43 bears against an eccentric 44 securedon an eccentric shaft 45 extending forwardly across the case beneath thefloor 23 and terminating in a knurled head 46. Thus, by rotating thehead 46 in one direction, the rod 31 can be forced upwardly to cause thelifting yokes l1 to engage the studs l and lift the knife edges l4 fromtheir bearing agates 311. The amount of lift should be exceedinglysmall, possibly two thousandths of an inch, so that very little swingingmovement is imparted to the pans The amount of lift can be easilyadjusted by means of the adjustable lift screw 43. It is also essentialthat the lifting yokes |1 ascend in accurate vertical alignment with thestuds I6 so that no sideward movement will be imparted to the beam. Thisvertical alignment is attained by means of a guide post 41 which extendsdownwardly through an enlarged opening 48 in the angle member 21. Acontact screw 49 is threaded into each side of the angle member intocontact with the post 41. By relative adjustment of these screws, thelifting yokes H can be accurately aligned with the studs It. Thehorizontal bracket member 36 is perforated for the passage of thebearing posts and is entirely free therefrom.

The simplicity of the beam support and its lifting mechanism is apparentto anyone skilled in the art. All of the accurate drilling and reamingfor the lifting rod and the accurate machining of the lifting rod hasbeen entirely eliminated. The diameters of the rod are unimportant sinceit will always find a vertical bearing against the angular surfaces 39and no drilling or reaming is necessary Any looseness that may developin the usual construction requires entire rebuilding. Any loosenesswhich may develop in this construction can be quickly taken up by simplyadjusting the screws 42. It is also desired to call attention to thefact that no floor space is occupied by any beam supporting mechanism.All supporting is accomplished from the rear wall of the case.

The lifting mechanism and its bearings are concealed and protected bymeans of a channelshaped cover plate 50. The cover plate is formed witha hinge rod 5| extending across its channel at the top thereof whichengages in a receiving notch 52 in a projecting boss 53 on the member24. To place the cover plate in place, it is only necessary to engagethe rod 5| in the slot 52 and then swing the cover plate inwardly. Thesides of the plate frictionally engage the two sides of the member 24which are extended outwardly to enclose the lift rod and channel. Thevertical edges of the cover plate 50 extend into vertical grooves 54formed in the member 24 so as to form a concealed joint with thesupporting member 24.

While a specific form of the improvement has been described andillustrated herein, it is desired to be understood that the same may bevaried, within the scope of the appended claims, without departing fromthe spirit of the invention.

Having thus described the invention, what is claimed and desired securedby Letters Patent is:

1. In a laboratory balance, the combination with a case having sidewalls, a back wall, a top, and a floor, a supporting member at themidportion of said back wall; a bracket member extending forwardly intothe case from said supporting member; means for supporting a scale beamfrom said bracket member; vertically aligned bearings on the rear ofsaid supporting member; a lifting rod vertically slidable in saidbearings; a beam lifting arm fixed to said lifting rod at its upperextremity and extending forwardly through said supporting member abovesaid bracket member, and means on said lifting arm for lifting a beamfrom its bearings on said bracket member.

2. In a laboratory balance, the combination with a case having sidewalls, a back wall, a top, and a floor, a supporting member forming themid-portion of said back wall; a bracket member extending forwardly intothe case from said supporting member; means for supporting a scale beamfrom said bracket member; vertically aligned bearings on the rear ofsaid supporting member; a lifting rod vertically slidable in saidbearings; a beam lifting arm fixed to said lifting rod at its upperextremity and extending forwardly through said supporting member abovesaid bracket member, and means on said lifting arm for lifting a beamfrom its bearings on said bracket member; each of said verticallyaligned bearings comprising, a channel open on the rear of saidsupporting member, oppositely inclined vertical side walls in saidchannel against which said rod rests, and means for holding said rodagainst said inclined side walls.

3. In a laboratory balance, the combination with a case having sidewalls, a back wall, a top, and a floor, a supporting member forming themid-portion of said back wall; a bracket member extending forwardly intothe case from said supporting member; means for supporting a scale beamfrom said bracket member; vertically aligned bearings on the rear ofsaid supporting member; a lifting rod vertically slidable in saidbearings; a beam lifting arm fixed to said lifting rod at its upperextremity and extending forwardly through said supporting member abovesaid bracket member, means on said lifting arm for lifting a beam fromits bearings on said bracket member; each of said vertically alignedbearings comprising, a channel open on the rear of said supportingmember, oppositely inclined vertical side walls in said channel againstwhich said rod rests; a cover member extending across each channel, andan adjusting screw in each cover member for urging said rod against saidinclined side walls.

4. In a laboratory balance, the combination with a case having sidewalls, a back wall, a top,

and a floor, a supporting member forming the mid-portion of said backwall; a bracket member extending forwardly into the case from saidsupporting member; means for supporting a scale beam from said bracketmember; vertically aligned bearings on the rear of said supportingmember; a lifting rod vertically slidable in said bearings; a beamlifting arm fixed to said lifting rod at its upper extremity andextending forwardly through said supporting member above said bracketmember, means on said lifting arm for lifting a beam from its bearingson said bracket member; each of said vertically aligned bearingscomprising, a channel open on the rear of said supporting member,oppositely inclined vertical side walls in said channel against whichsaid rod rests; a bearing strap extending vertically against said rodopposite said inclined side walls, and means for holding said bearingstrap against said rod.

5. In a laboratory balance, the combination with a case having sidewalls, a back wall, a top and a floor of a supporting member forming themid-portion of said back wall; a bracket member extending forwardly intothe case from said supporting member; and means for supporting a scalebeam from said bracket member, vertically aligned bearings on the rearof said supporting member; a lifting rod vertically slidable in saidbearings; a beam lifting arm fixed to said lifting rod at its upperextremity and extending forwardly of said supporting member above saidbracket member, and means on said lifting arm for lifting a beam fromits bearings on said bracket member, each of said vertically alignedbearings comprising, a channel open on the rear of said supportingmember, oppositely inclined, vertical side walls in said channel againstwhich said rod rests, a bearing strap extending vertically against saidrod opposite said inclined side Walls, means for holding said bearingstrap against said rod, said rod and its bearing channels being exposedon the rear of said supporting member on the exterior of said case, anda removable cover plate concealing the same.

6. Means for supporting the bearings of a laboratory scale beam andmeans for lifting said beam from its bearings comprising: a verticalsupporting member; a bracket extending from said supporting member;bearing means carried by said bracket for said scale beam; an inverted,L-shaped lifting member having a horizontal, upper leg and a verticallifting rod fixedly joined at right angles to each other, the liftingrod extending between said beam and said bracket member and carryingmeans for lifting the beam, the rod extending vertically along one faceof the supporting member in a receiving channel therein; oppositelyinclined side walls in said channel against which said rod bears alongvertical lines; means for holding said rod against said side walls; andmeans for lifting said rod.

7. Means for supporting the bearings of a laboratory scale beam andmeans for lifting said beam from its bearings comprising: a verticalsupporting member; a bracket extending from said supporting member;bearing means carried by said bracket for said scale beam; an inverted,L-shaped lifting member having a horizontal, upper leg and a verticallifting rod fixedly joined at right angles to each other, the liftingrod extending between said beam and said bracket member and carryingmeans for lifting the beam, the rod extending vertically along one faceof the supporting member in a receiving channel therein; oppositelyinclined side walls in said channel against which said rod bears alongvertical lines; a cover plate extending across said channel; anadjusting screw in said cover plate for urging said rod against itsinclined side walls; and means for lifting said rod.

FRED W. THOMPSON.

